300 THE AMERICAN MONTHLY [Nov 
Sarcophaga Carnaria, Longitudinal Section cf Halter.— 
These sections show the vascular tissue in the so-called 
globe of the halter. In all the halteres I have examined 
the deep invagination seen in these sections of the globe 
is invariably present, and there is always a mass of con- 
nective tissue extending from the invaginated wall to the 
opposite wall of the globe. The purpose of the invagi- 
nation is unknown to me, unless by some means it allows 
of a certain amount of expansion and contraction of the 
globe. The large glands most probably secrete a fluid 
necessary for organs at the base of the halter. The hal- 
teres of Diptera doubtless assist in their locomotion, but 
the evidence of their elaborate structure proves that they 
have another most important function. The positions of 
the papille are such as to present a front in every direc- 
tion, and their structure is so delicate as to permit of vi- 
bration when sound-waves or other unusual movements 
of the air impinge upon them. Also the nerve epithelium 
bathed in fluid secreted in the globe, together with the 
very rich nerve supply, point to their being rudimentary 
nerve organs. Otoliths, so commonly found in the Crus- 
tacea and Mollusca, I have not met with here, but that 
does not prove their non-existence. The great number 
of papillew (400 to 500) in each halter, and the small num- 
ber of olfactory organs (two in each antenna) found in 
many flies which feed on the nectar of flowers, compared 
with UM. vomitoria and M. domestica, whose halteres carry 
half the number of papilla, and in whom the olfactory 
sense is highly developed, show that the former possess 
an acute sense to warn them of danger when their heads 
are buried in the blossoms of the plants they frequent, 
and that the latter have comparatively little use for such 
a sense. 
Anterior Thoracic Spiracle of Blow-fly.—This spiracle is 
oval and narrowest above, and is situated between the 
